Klingon augment virus
The Klingon augment virus was a modified form of Levodian flu that threatened to wipe out the Klingon race in the middle 22nd century. In 2154, Klingon scientists working under the direction of Antaak recovered some DNA from a destroyed Bird of Prey that had been earlier hijacked by human augments created by Arik Soong. Fearful that humans would create augments and overwhelm the Empire, the scientists attempted to create their own augments to counter the percieved threat. The effort failed dreadfully. The augments created did develop enhanced strength and intelligence, but they also began to show human characteristics, from the blatant to the subtle. These included loss of the characteristic forehead ridges and personality alterations. Ultimately, the subjects died agonizing deaths when the incompatible DNA resulted in neural system breakdown. While working to stabilize the process of augmentation, the scientific team augmented a test subject who was, unknown to the team, also infected with Levodian flu. The flu virus in some manner incorporated the augment DNA, turning a carefully controlled experiment into an epidemic. Inasmuch as the unstable augmentation process always killed the subject, this epidemic threatened the Klingon race with extinction. Their efforts to capture Arik Soong thwarted by his high security detention, the Klingons next arranged, through Rigellian intermediaries, to kidnap Phlox. He worked with Antaak to stabilize the augment virus. Antaak's goal was to create a stable method of creating Klingon augments, Phlox's goal was to cure the plague before the Klingons died as a species. Ultimately, the goal achieved lay somewhere in the middle: a method was created that stabilized the process in the early stages -- after the cranial ridges dissolved, but before the personality changes and fatal neural path breakdown. Because afflicted Klingons' DNA had been altered by the virus, they passed this trait onto their descendants. It would be nearly a hundred years before the Klingons discovered a method of reversing the effect and restoring all Klingons to their proper appearance and genetic code. Evidently, this event was not widely reported on Earth or to her eventual allies in the Federation. By the 23rd century, the reason for smooth forehead Klingons was not widely known outside the Empire, and questions were generally met with a brusque answer along the lines of "we don't discuss it". (ENT: "Affliction", ENT: "Divergence", DS9: "Trials and Tribble-ations]]") This storyline was constructed to explain why original series Klingons had smooth foreheads, and later Klingons did not. Fans have speculated that altered Klingons did, in fact, develop some personality changes, and that this is why the emphasis on honor seen in more recent Klingons was notably lacking from Original Series era Klingons. Retroviruses often incorporate bits and pieces of the DNA of cells they infect into their own genetic structure, prior to co-opting the cellular machinery for their own use. The copies of such viruses sometimes pass this DNA onto cells THEY infect. By this method, DNA from one organism can be transformed to another; it is now thought that this might be one mechanism of evolution. Microorganisms that have developed immunity to antibiotics are thought in some cases to have developed it through this sort of DNA sharing. Alien DNA incorporated into cells of larger organisms generally has far less effect, since such cells are vastly outnumbered by "normal" cells.